In the related art, there is known a liquid droplet ejecting apparatus including an apparatus body that includes a liquid ejecting head and a sub-tank and a cartridge that includes a liquid chamber and is detachably installed on the apparatus body (for example, see JP-A-2008-213162).
When ink flows from the sub-tank to the liquid ejecting head, the ink flows from the liquid chamber of the cartridge to the sub-tank. The sub-tank and the liquid chamber are both opened to the atmosphere. Thus, a liquid level of the ink in the sub-tank and a liquid level of the ink in the liquid chamber of the cartridge are at the same height in the end.
In the liquid droplet ejecting apparatus, a detection object for detecting a remaining amount of liquid in the liquid chamber is inside the liquid chamber of the cartridge.
In the liquid droplet ejecting apparatus disclosed in JP-A-2008-213162, a remaining amount of ink of the cartridge is detected, but a remaining amount of ink in the sub-tank is not determined. Accordingly, when a user is informed that the remaining amount of ink in the cartridge is zero or equal to or less than a predetermined amount, it is necessary to immediately exchange the cartridge. However, even after the ink stored in the cartridge is used up, the ink is stored in the sub-tank. Therefore, there is ink to be consumed for image recording or the like. When a user is informed that the sub-tank is empty on the assumption that the ink stored in the sub-tank can be used, the remaining amount of ink in the cartridge is zero or equal to or less than a predetermined amount. Image recording or the like can be performed even later. As a result, the user has an enough time available to exchange the cartridge. On the other hand, when the ink stored in the sub-tank is completely consumed, air flows from the sub-tank to a recording head. Thus, an ejection failure occurs in the recording head or a large amount of ink is assumed for maintenance to recover the ejection failure in some cases. Accordingly, it is necessary to determine the remaining amount of ink in the sub-tank with high precision so that air does not flow in the recording head.